This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to Appln. No. 01810641.9 filed in Europe on Jul. 2, 2001; the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The invention relates to a fire prevention safety device for gas meters according to the preamble of patent claim 1. The fire prevention safety device is suitable in particular for gas meters in the domestic sector.
2. Background of the Invention
In the event of a fire, it is necessary to prevent the gas emerging from gas lines and increasing the risk of explosion. One known weak point is gas meters, which are arranged in the gas line itself or in a secondary line or a bypass thereto.
Instead of the known bellows gas meters use is increasingly being made of electronic gas meters. These electronic gas meters have sensors which are arranged in a protected manner in a housing. In order to satisfy the fire regulations, these housings and the electrical leadthroughs through the housing have to withstand high thermal stresses. This increases the material and production costs of such gas meters tremendously. However, since they are also to be used in the domestic and small commercial sector, minimization of costs is necessary.
Furthermore, U.S. Pat. No. 6,129,105 discloses an interrupter for a gas meter which is used in the event of a gas leak and/or in a prepayment system. The interrupter is arranged in a gas meter and adjoins a gas pipe. It has a spring-loaded valve with a diaphragm which interrupts the gas supply. Since this diaphragm melts in the event of a fire, it is arranged on a support element made of metal which, in the event of a fire, takes over the sealing function. The valve is spring-loaded and has a safety fuse, so that in the event of a fire it is pressed against the gas pipe by spring force and closes the pipe. This interrupter is relatively complicated and accordingly expensive.
It is therefore an object of the invention to provide a fire prevention safety device for gas meters which is simple and cost-efficient but effective.
This object is achieved by a fire prevention safety device having the features of patent claim 1.
In the fire prevention safety device according to invention, the gas meter is arranged in a bypass of a gas pipe, wherein at least one closure means, that can be activated by heat to interrupt the gas supply, is arranged in the bypass in the flow direction upstream and downstream of a sensor belonging to the gas meter.
As a result of arranging the closure means in the bypass, only a relatively small flow aperture has to be closed. In addition, it is not necessary for the gas meter itself to meet the high requirements on the ability to withstand a thermal load in the event of a fire, for example those placed by the HTB standard. It is sufficient if the bypass closed by the closure means according to invention meets the requirements. This fire protection safety device can be used in particular for gas pipe with electronic gas meters in the domestic and small commercial sector, since it is cost-efficient and can be installed with ease.
In a preferred embodiment, the closure means has a closure element of swelling or expandable material. In a preferred variant, the closure means consists completely of this swelling or expandable material.
In another preferred embodiment, the closure means has a spring-loaded valve piston for closing the bypass, the valve piston being held in its prestressed position by a securing element. The securing element is preferably a safety fuse or a bimetallic retainer.
Further advantageous variants of the method and advantageous embodiments emerge from the dependent patent claims.